Jeff let out a loud groan of pain and pleasure as he felt the dick inside him swell, the hard rod getting longer and thicker. He looked back and gasped in shock as he saw the monstrous muscles of the mailman. The postal employee was growing larger with each thrust it seemed, veins rising all over his throbbing, swelling muscles. His posers had snapped off, unable to stretch any more as the mailman's thighs grew too large to be contained.
"Oh fuck..." Jeff breathed, feeling the bed tremble beneath him, the headboard going back and forth and banging against the wall due to the vigor of the mailman's thrusts. The hulking brute wrapped a giant arm around Jeff, pulling the smaller man up against his swollen pecs, his hard stomach.
"Ohhh yeah..." the mailman groaned, his voice low and thick and rich. With Jeff firmly secured by a powerful arm, the hulking brute cut loose. He ravaged Jeff's ass, pounding his dick into it hard and deep, growling with bestial lust. Jeff gasped with pleasure, his ass stretched to adjust the muscleman's giant cock. "Gonna fill you up..." the mailman growled, his huge muscles tensing as orgasm neared.
With a loud roar the massive man came, his giant dick going wild inside Jeff, spasming violently as it shot a huge load of cum into Jeff's tight ass. Every one of the mailman's huge muscles flexed, swelling dramatically, adding more and more mass by the second. The hulking brute took huge breaths, his giant chest expanding behind Jeff's head, the two massive slabs of beef threatening to squeeze the teen's head between them as they swelled big enough to engulf the back of it. It was too much for Jeff. His own dick sprayed cum all over the sheets below him as he moaned with pleasure.
The mailman's thrusts ceased. He held position for several minutes, his huge dick buried deep in Jeff's ass, leaking cum. When there was no more seed left, he slowly pulled out, producing a soft gasp from the smaller man.
The hulking muscleman slid off the bed, the frame creaking under him. The metal had bent in several places, and there were holes in the drywall from where the headboard had hit. Jeff slowly rolled onto his side, his ass aching delightfully. He looked up at the mailman and gasped in shock. He had seen the man grow during sex, but only now realized the extent of it. The man had to be at least seven feet tall, and was easily more than five hundred pounds, all of it muscle. Jeff's eyes roamed the vast landscape of the mailman's huge body. He nearly choked on his own tongue when he saw the enormous tool that hung between the mailman's giant thighs. It was big, even when compared to the enormous body it was attached to. When compared to Jeff, it was as big as the smaller man's forearm. It rested above a scrotum that was packed with nuts so big they were nearly the size of baseballs.
The mailman stood beside the bed, running his hands up and down his bloated musculature. "mmmm... fuck that was nice..." he purred.
The very sound of his voice sent a shiver of lust through Jeff. He tried to focus, to think about what had just happened. The mailman had already grown when he first encountered Jeff. But sex seemed to produce a second round of growth. And the results were beyond impressive. Jeff tried to wrap his head around the implications of that.